Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quem veio como substituto no Sheffield United?
 ###Tabelas: CREATE TABLE top_attendances (top_attendances_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Round VARCHAR, Home team VARCHAR, Away team VARCHAR, Result VARCHAR, Location VARCHAR, Attendance INT) CREATE TABLE average_scores_of_all_couples (average_scores_of_all_couples_id AUTO_INCREMENT PRIMARY KEY, Rank by average VARCHAR, Place VARCHAR, Perfect 40s VARCHAR, Total VARCHAR, Number of dances VARCHAR, Season VARCHAR, Average VARCHAR) CREATE TABLE oklahoma_counties_ranked_by_per_capita_income (oklahoma_counties_ranked_by_per_capita_income_id AUTO_INCREMENT PRIMARY KEY, County VARCHAR, Per capita income VARCHAR, Median household income VARCHAR, Median family income VARCHAR, Population INT, Number of households INT) CREATE TABLE season_20:_2012-2013 (season_20:_2012-2013_id AUTO_INCREMENT PRIMARY KEY, Series Ep. VARCHAR, Episode INT, Segment A VARCHAR, Segment B VARCHAR, Segment C VARCHAR, Segment D VARCHAR) CREATE TABLE managerial_changes (managerial_changes_id AUTO_INCREMENT PRIMARY KEY, Team VARCHAR, Outgoing manager VARCHAR, Manner of departure VARCHAR, Date of vacancy VARCHAR, Replaced by VARCHAR, Date of appointment VARCHAR, Position in table VARCHAR)  
SELECT Replaced by FROM managerial_changes WHERE Team = Sheffield United